# Vertical Interconnection Technology for RF MicroSystem Packaging

## TL;DR

This paper presents a new vertical interconnection technology for RF microsystems that improves performance and reliability for millimeter-wave communication.

## Contribution

A novel 1.5-level interconnection method with optimized solder ball structures for RF microsystem packaging is introduced.

## Key findings

- Optimized SAC305 and Sn63Pb37 solder balls improve RF performance and reliability.
- Numerical models using HFSS validated the effectiveness of the interconnection structures.
- Manufactured samples demonstrated high reliability using the optimized integration process.

## Abstract

In this work, 1.5-level interconnections of RF microsystems with good RF performance, integration process compatibility, and high reliability are developed to meet the future demand for wireless communication microsystems in the millimeter wave band. Numerical models of 1.5-level interconnections based on solder balls with different diameters are established and analyzed using HFSS. The optimized structure parameters of 0.2 mm diameter Sn96.5Ag3Cu0.5 (SAC305) solder balls and 0.3 mm diameter Sn63Pb37 solder balls are selected for the interconnection between glass micro substrates and silicon micro substrates and between silicon micro substrates and HTCC substrates, respectively. Integration process parameters of the vertical interconnection are optimized. The micro substrate interconnection samples manufactured based on optimized integration methods and parameters show high reliability.